1. Field of the Invention
The present invention relates to a coolant and, more particularly, to a coolant for a cooler box to be used for the preparation, mainly at home, of frozen sweets, such as ice creams and sherbets, and the transportation or delivery, while being cooled, of processed foods or frozen foods, as well as for leisure purposes. In another aspect, it relates to a coolant having an anticorrosion effect for a metal container in which it is to be enclosed.
2. Description of the Prior Art
Upon preparation, at home, of frozen sweets, such as ice creams and sherbets, there have been used a combination of an outer container charged with a mixture of salt and ice, and an inner container placed in the outer container and charged with materials for preparing ice creams. For preparing a frozen sweet by such a combination of containers, however, a long period of time is required because of its low cooling capacity due to its limited cntact area between the inner container and the mixture of salt and ice.
It has been proposed to use a double walled container with a liquid coolant having a certain composition enclosed within its walls. An example of such a coolant is disclosed in Japanese Patent Application (Laid Open) No. 131,687/84, which is consisting of a mixture of an aqueous 16 to 18% solution of potassium hydrogencarbonate or potassium bicarbonate and 2 to 10%, based on the aqueous solution, of ethyl alcohol.
However, the known coolant has the following disadvantages. Its freezing point is not satisfactorily low. To be more specific, its freezing point could be hardly lower than -8.5.degree. C. even when it has an increased ethyl alcohol content. Potassium hydrogencarbonate contained therein is not stable enough not to be decomposed when exposed to heat. There is also a tendency that bubbles are generated upon the mixing of the aqueous solution of potassium hydrogencarbonate with ethyl alcohol. Because of this bubbling phenomenon, the coolant, when used in a closed container, often causes the deformation of its container. In addition, the coolant, when used in a metal container, causes the corrosion of its container after a long period of time.